1. Field
This disclosure relates to interlock assemblies which can be used to prevent main and branch circuit breaker in a panelboard from being simultaneously in the “ON” position. In particular, the unique interlock assembly is particular with a generator panel or ATS (automatic transfer switch) switch when alternative power sources are used by customer to support critical loads in the event of failure of utility power supply.
2. Discussion of the Background Art
Mechanical interlocks which interconnect a pair of lever operated switches are well known. In circuit breaker panelboards, one such interlock has been mounted on the cover and has slidably interacted with the operator handles of tandemly (transversely) mounted circuit breakers. However, the interlock function is removed with the cover when servicing the panelboard in this version. Another panelboard has a sliding interlock mounted on a bracket which extends along the longitudinal center line of the panel. The ends of the bracket extend along the sides of the respective circuit breakers and are bolted directly to the panel or to the enclosure. One end of the bracket is offset from the center of the panel to clear a bus bar of the panelboard. A different length bracket is required for each panel accepting a different number of circuit breakers which translates into a different length for the panel. It is also necessary to modify the cover opening for the circuit breakers by notching the opening to receive the bracket at each end of the row of circuit breakers since the bracket extends beyond the side surface of the end circuit breakers. Thus, special covers are provided on panelboards or loadcenters utilizing this version of sliding interlock. The provision of special parts increases the cost of the item, both to manufacture and contractors to stock the different parts.
One such conventional interlock assembly is set forth in U.S. Pat. No. 5,393,942 to Reiner et al., which discloses a mechanical interlock for the operator handles of two main circuit breakers mounted in a panelboard or loadcenter. The interlock mounts transversely of the interior panel and therefore is not dependent upon the length of the interior panel. The interlock requires no special modification of any parts of the loadcenter or panelboard, thereby using all standard parts. The interlock attaches to the mounting rails of the interior panel by screw fasteners or the like and therefore can be used to provide a hold-down function for the main circuit breakers, thereby eliminating separate components for this function. The interlock slide may also be provided with padlock hasps whereby the operator handles of one or both of the circuit breakers can be locked in the OFF position by inserting the padlock shackle through the appropriate hasp of the interlock slide.
The problems associated with conventional interlock kits which convert panelboards to generator panels are that (1) they require ordering of separate front/shield to suit the interlock assemblies; (2) the interlock assemblies are costly due to intricate design involving large part counts, including auxiliary breaker retainers; and (3) convention interlock assemblies are difficult to install.
Additionally, the interlock assembly according to the present disclosure is not movably mounted on a bracket attached to mounting rails transversely of the panelboard. To the contrary, the present disclosure pertains to a novel interlock assembly that mounts directly to the panel deadfront.
The interlock assembly according to the present disclosure has the following advantages over conventional interlocks, i.e., (1) it is field installable to convert existing panelboards (loadcenter/meter socket loadcenter) into generator panels to support critical loads in residential applications utilizing alternate power sources, (2) its unique configuration allows for mounting directly over the deadfront/shield of a panelboard, (3) it interacts with breaker handles of main and auxiliary breaker to make sure only one breaker is in the “ON” position, and (4) it allows for both the main and auxiliary breakers to be put in the “OFF” position.
The present disclosure also provides many additional advantages, which shall become apparent as described below.